1. Field of the Invention
The present invention relates generally to internal combustion engines, and particularly to a two-stroke reciprocating internal combustion engine having an internal structure that precludes oil mixing with the intake air charge.
2. Description of the Related Art
The reciprocating internal combustion engine has been the mainstay of motive power plants for a considerable period of time, due to its relative size and weight for its power output, fuel economy, and ease of operation. Nevertheless, such engines have their drawbacks. For example, the two-stroke engine in which both the exhaust and compression portions of the cycle occur during the upstroke of the piston and the power and intake strokes occur during the downstroke of the piston, is well known to produce relatively high power output for its size and weight due to the efficiency of a power stroke at every revolution of the crankshaft. However, such engines have historically been relatively inefficient insofar as fuel consumption and emissions production are concerned due to the lack of separation of the four distinct phases of the cycle with each having its own stroke, as in the conventional four-stroke (Otto cycle) engine.
Another problem with the two-stroke engine is that conventionally such engines initially draw the intake charge into the crankcase, whereupon the downstroke of the piston on the power stroke pressurizes the crankcase to force the intake charge into the cylinder for the next power stroke. As the crankcase is essentially continually filled with air, the conventional oil-filled crankcase used in the lubrication of the four-stroke engine cannot be used for lubrication of the two-stroke engine. Accordingly, oil is either mixed with the fuel during refueling, or oil is injected into the engine during operation, with two-stroke engines. Either system results in oil contamination of the air-fuel mixture as it passes through the engine, is burned to produce power, and passes out of the engine as exhaust. The present day requirement to reduce engine emissions precludes the use of such an engine operating principle in most applications, even though the relatively high power output of such engines for their weight can result in a desirable reduction of the weight of the vehicle in which it is installed.
Thus, a two-stroke engine solving the aforementioned problems is desired.